Tunable inductor arrangement, transceiver, method and computer program

ABSTRACT

A tunable inductor arrangeable on a chip or substrate comprises a first winding part connected at one end to a first input of the tunable inductor arrangement, a second winding part connected at one end to the other end of the first winding part, a third winding part connected at one end to a second input of the tunable inductor arrangement, a fourth winding part connected at one end to the other end of the third winding part, and a switch arrangement arranged. The switch arrangement tunes the tunable inductor by selectively connecting the first and fourth winding parts in parallel and the second and third winding parts in parallel, with the parallel couplings in series between the first and second inputs, or connecting the first, second, fourth and third winding parts in series between the first and second inputs. Corresponding transceivers, communication devices, methods and computer programs are disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/360,414 filed 21 Mar. 2019, which is a continuation of U.S.application Ser. No. 15/872,184 filed 16 Jan. 2018, now U.S. Pat. No.10,283,252, which is a continuation of U.S. application Ser. No.15/029,284 filed 14 Apr. 2016, now U.S. Pat. No. 9,905,350, which is aNational Phase application of PCT/EP2014/071750 filed 10 Oct. 2014,which claims priority from EP13188910.7 filed 16 Oct. 2013. The entirecontents of each aforementioned application is incorporated herein byreference.

TECHNICAL FIELD

The present invention generally relates to a tunable inductorarrangement, a radio frequency transceiver or receiver with a resonatorhaving such an arrangement, a communication device, a method of tuningthe arrangement and a computer program for tuning.

BACKGROUND

As more bands are to be supported in radio transceivers, which bands mayspan over a wide frequency range such as from 600 MHz to 3800 MHz, thiscan be met by a set of resonators. It is known that tuning an LC(inductor-capacitor) resonator more than one octave is difficult, whichgives that a multitude of resonators may be demanded. This problem isfurther emphasized when carrier aggregation, i.e., the communication isperformed on several different carriers simultaneously, which carriersmay be spread anywhere in the wide frequency range.

LC resonators consume chip space, when implemented on-chip, and arefairly costly when implemented off-chip. It is, therefore, a desire toprovide more flexible resonators.

SUMMARY

An object of the invention is to at least alleviate the above-statedproblem. The present invention is based on the understanding that bothcapacitance and inductance of an LC resonator need to be tuned toachieve the desired flexibility. A tunable inductor arrangement isprovided accordingly. The inventor has also realized the demands thatthe self-resonant frequency needs to be set high enough forhigh-frequency modes, the Q-value has to be high enough not to degradegain or increase current consumption in a usable implementation, andthat the ratio of the inductances needs to be high enough to also coverthe low bands. This is achieved by a switch arrangement in the tunableinductor arrangement which performs signal routing such that insertionloss is decreased.

According to a first aspect, there is provided a tunable inductorarrangement arrangeable on a chip or substrate. The tunable inductorcomprises a first winding part connected at a first end to a first inputof the tunable inductor arrangement; a second winding part connected ata first end to a second end of the first winding part; a third windingpart connected at a first end to a second input of the tunable inductorarrangement; a fourth winding part connected at a first end to a secondend of the third winding part; and a switch arrangement arranged to tunethe tunable inductor arrangement by selectively provide any of a circuitcomprising the first and fourth winding parts in parallel and the secondand third winding parts in parallel, with the parallel couplingsconnected in series between the first and second inputs; and a circuitcomprising the first, second, fourth and third winding parts in seriesbetween the first and second inputs.

The switch arrangement may comprise a first switch connected between asecond end of the second winding part and a virtual ground; a secondswitch connected between the second end of the fourth winding part andthe virtual ground; a third switch connected between the first end ofthe second winding part and the virtual ground; a fourth switchconnected between the first end of the fourth winding part and thevirtual ground; a fifth switch connected between the first input and asecond end of the fourth winding part; and a sixth switch connectedbetween the second input and the second end of the second winding part.The tunable inductor arrangement may then be tunable by either closingthe third, fourth, fifth and sixth switches and having the first andsecond switches open, or closing the first and second switches andhaving the third, fourth, fifth and sixth switches open.

The switch arrangement may comprise a first switch connected between asecond end of the second winding part and a second end of the fourthwinding part; a second switch connected between the second end of thefirst winding part and the second end of the third winding part; a thirdswitch connected between the first input and the second end of thefourth winding part; and a fourth switch connected between the secondinput and the second end of the second winding part. The tunableinductor arrangement may then be tunable by either closing the second,third and fourth switches and having the first switch open, or closingthe first switch and having the second, third and fourth switches open.

The first, second, third and fourth winding parts may be interleaved onthe chip or substrate such that magnetic fields of the windings areessentially common.

The tunable inductor arrangement may comprise a further winding partwherein the further winding part is arranged to cancel electromagneticcoupling with the first to fourth winding parts.

Two or more of the winding parts may be arranged in a plurality ofconductive layers on the chip or substrate.

The virtual ground may be a DC power supply, which at AC, such as radiofrequency, acts as a ground for AC signals, or be a ground or DCreference voltage node.

According to a second aspect, there is provided a radio frequencytransceiver comprising a resonator, wherein the resonator comprises atunable inductor arrangement according to the first aspect, wherein thetunable inductor arrangement is tunable to enable the resonator toselectably work at one of a plurality of resonating frequencies.

According to a third aspect, there is provided a multiband radiofrequency receiver comprising a first receiver path arranged to receivea radio signal in a first frequency band; a second receiver patharranged to receive a radio signal in a second frequency band, whereinthe first frequency band operates at a higher frequency than the secondfrequency band, and each of the first and second receiver paths isarranged to selectively operate at a selected frequency band among aplurality of frequency bands; and comprises a resonator comprising atunable inductor arrangement according to the first aspect, whichresonator is arranged to be tuned for the selected frequency band.

According to a fourth aspect, there is provided a communication devicecomprising a radio frequency transceiver according to the second aspector a multiband radio frequency receiver according to the third aspect,and a processor arranged to interact with the radio frequencytransceiver or multiband radio frequency receiver, wherein the processoris arranged to control to the switch arrangement to select a tuning modeof the tunable inductor arrangement.

According to a fifth aspect, there is provided a method of a tunableinductor arrangement including winding parts and switches for tuningaccording to the first aspect. The method comprises determining a tuningsetting for the tunable inductor arrangement; assigning switch statesfor respective switches for the tuning setting; and controlling theswitches according to the assigned switch states.

According to a sixth aspect, there is provided a computer programcomprising computer executable instructions which when executed by aprogrammable controller of a radio frequency transceiver or multibandradio frequency receiver comprising a resonator which comprises atunable inductor arrangement causes the controller to perform the methodof the fifth aspect.

Other objectives, features, and advantages of the present invention willappear from the following detailed disclosure, from the attacheddependent claims as well as from the drawings. Generally, all terms usedin the claims are to be interpreted according to their ordinary meaningin the technical field, unless explicitly defined otherwise herein. Allreferences to “a/an/the [element, device, component, means, step, etc.]”are to be interpreted openly as referring to at least one instance ofsaid element, device, component, means, step, etc., unless explicitlystated otherwise. The steps of any method disclosed herein do not haveto be performed in the exact order disclosed unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features, and advantages ofthe present invention, will be better understood through the followingillustrative and non-limiting detailed description of preferredembodiments of the present invention, with reference to the appendeddrawings.

FIG. 1 schematically illustrates a tunable inductor arrangementaccording to an embodiment.

FIG. 2 illustrates a layout of windings of a tunable inductorarrangement together with a schematic indication on the switcharrangement according to an embodiment.

FIG. 3 illustrates a layout of windings of a tunable inductorarrangement when switches are in a first state, as illustrated in thecorresponding schematic to the right, according to an embodiment.

FIG. 4 illustrates a layout of windings of a tunable inductorarrangement when switches are in a second state, as illustrated in thecorresponding schematic to the right, according to an embodiment.

FIG. 5 illustrates a detail of a layout of windings of a tunableinductor arrangement according to an embodiment.

FIG. 6 schematically illustrates a radio front end where the tunableinductor arrangements according to embodiments are applicable.

FIG. 7 is a block diagram schematically illustrating a communicationdevice according to an embodiment.

FIG. 8 is a flow chart schematically illustrating a method of a tunableinductor arrangement according to an embodiment.

FIG. 9 schematically illustrates a computer program and a processor forimplementing the method.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a tunable inductor arrangementaccording to an embodiment. The inductor arrangement is preferablyarranged on a chip or substrate, as will be demonstrated below. Thetunable inductor arrangement comprises a first winding part W1 connectedat one end to a first input INP of the tunable inductor arrangement, asecond winding part W2 connected at one end to the other end of thefirst winding part W1, a third winding part W3 connected at one end to asecond input INN of the tunable inductor arrangement and a fourthwinding part W4 connected at one end to the other end of the thirdwinding part. A switch arrangement is arranged to tune the tunableinductor arrangement by selectively provide for that a circuitcomprising the first and fourth winding parts W1, W4 in parallel and thesecond and third winding part W2, W3 in parallel, and then couple therespective parallel couplings W1, W4; W2, W3 in series between the firstand second inputs INP, INN, or a circuit comprising the first, second,fourth and third winding parts W1, W2, W4, W3 in series between thefirst and second inputs INP, INN. The switch arrangement comprises afirst switch S1 connected between the other end of the second windingpart W2 and a virtual ground VDD, a second switch S2 connected betweenthe other end of the fourth winding part W4 and the virtual ground VDD.The virtual ground may be a DC power supply, thus here named VDD, whichat AC, such as radio frequency, acts as a ground for AC signals, or be aground or DC reference voltage node. If the center tap is not used, thefirst and second switches can be substituted by a single switch S12providing the same function as the first and second switches S1, S2. Theswitch arrangement further comprises a third switch S3 connected betweenthe other end of the first winding part W1 and the virtual ground VDD,and a fourth switch S4 connected between the other end of the thirdwinding part W3 and the virtual ground VDD. Similar, when the center tapis not used, the third and fourth switches can be substituted by asingle switch S34 providing the same function as the third and fourthswitches S3, S4. The tunable inductor arrangement is thereby tunable byeither closing the first and second switches S1, S2 (or the singleswitch S12) such that a circuit from the first input INP via the firstwinding part W1, the second winding part W2, the closed first switch S1,the closed second switch S2 (or the single switch S12), the fourthwinding part W4 and the third winding part W3 to the second input INN isformed, i.e., all the windings W1-W4 are coupled in series.

To accomplish that all windings are operable in both modes, the switcharrangement further comprises a fifth switch S5 connected between theone end of the first winding part W1 and the other end of the fourthwinding part W4, and a sixth switch S6 connected between the one end ofthe third winding part W3 and the other end of the second winding partW2. The tunable inductor arrangement is thereby further tunable byclosing the fifth and sixth switches S5, S6 when the third and fourthswitches S3, S4 are closed. In that case, a circuit is formed from thefirst input INP via the closed fifth switch S5, the fourth winding partW4, the closed fourth switch S4, the closed third switch S3, the secondwinding part W2, and the closed sixth switch S6 to the second input INN.

Thereby, the tunable inductor arrangement is enabled to, by selectivelyprovide for that a circuit comprising the first and fourth winding partsW1, W4 in parallel and the second and third winding part W2, W3 inparallel, and then couple the respective parallel couplings W1, W4; W2,W3 in series between the first and second inputs INP, INN, or a circuitcomprising the first, second, fourth and third winding parts W1, W2, W4,W3 in series between the first and second inputs INP, INN, providedifferent inductances where all the windings are operable in both modes.

Although the above demonstrated tunable inductor arrangement can operateall windings in all its operating modes, it may still be combinable withadditional inductor arrangements which does not. Such combinations mayprovide further tunability. To achieve a good Q-value, all winding partswith mutual magnetic interaction are preferably in operation at allstates. One or more circuits as the one demonstrated above can be usedas building blocks to achieve a tunable inductor arrangement.

FIG. 2 illustrates a layout of windings of a tunable inductorarrangement together with a schematic indication on the switcharrangement according to an embodiment. The circuit corresponds to thosedemonstrated with reference to FIG. 1 , and the function for providingdifferent inductances is the same.

FIG. 3 illustrates a layout of windings of a tunable inductorarrangement when switches are in a first state, as illustrated in thecorresponding schematic to the upper right, according to an embodiment.At lower right, the equivalent circuit is drawn for simple understandingof the effect of the circuit. The circuit corresponds to the oneachieved by having the single switch S12 (or the first and secondswitches S1 and S2) of FIGS. 1 and 2 closed and the other switches S34(or S4, S4), S5, S6 open. Here, it can be seen that the series couplingprovides a winding going from the terminal INP through all theconductive lanes and ending at the terminal INN.

The windings are arranged on a substrate or chip. The substrate can alsobe a printed circuit board. A virtual ground node can also be applied,which is also elucidated below with reference to FIG. 4 . The virtualground, which may be a DC power supply VDD, which at AC, such as radiofrequency, acts as a ground for AC signals, or be a ground or DCreference voltage node, can be employed. When in the first state, theswitch S12 (or S1, S2) connects the virtual ground node.

FIG. 4 illustrates a layout of windings of a tunable inductorarrangement when switches are in a second state, as illustrated in thecorresponding schematic to the upper right, according to an embodiment.At lower right, the equivalent circuit is drawn for simple understandingof the effect of the circuit. The circuit corresponds to the oneachieved by having the single switch S12 (or the first and secondswitches S1 and S2) of FIGS. 1 and 2 open and the other switches closed.Here, it can be seen that a first parallel coupling starting from theterminal INP provides a winding going to meet a second parallel couplingat point A, which goes all the way to the terminal INN. At the couplingat point A, a virtual ground (not shown), such as power supply, can beconnected. The virtual ground may be a DC power supply, which at AC,such as radio frequency, acts as a ground for AC signals, or be a groundor DC reference voltage node. When in the second state, the switch S34(or S3, S4) connects the virtual ground node. As can be seen, whenconsidering FIGS. 3 and 4 , the virtual ground node cannot be employedas a single center tap in the layout of the windings as of FIGS. 3 and 4. However, for some layouts, i.e. where S12 (or S1, S2) and S34 (or S3,S4) are located adjacent to each other, which is depending on the numberof turns and the application of the turns in multiple metal layers, thelayout of the virtual ground node can be kept to one area of thesubstrate or chip.

FIG. 5 illustrates a detail of a layout of windings of a tunableinductor arrangement according to an embodiment. Crossings of conductivelanes forming the windings can thus be achieved. Two or more of thewinding parts can be arranged in a plurality of conductive layers on thechip or substrate. In the illustrations, the lanes are provided side byside on the substrate and the crossings using layered conductors.However, the lanes can also use layered conductors and be placed on topof each other, or a combination of be provided in different layers andside by side. The shape of the windings have also been illustrated as anoctagon, but other shapes are as feasible, such as circular, square, oranother n-sided shape, where n is 3 or higher, or combinations thereof,which form windings enclosing a magnetic field which is the purpose ofthe windings to form an inductance. The inductance can be adapted fordifferential purposes or single-ended purposes in a conventional way.

FIG. 6 schematically illustrates a radio front end where the tunableinductor arrangements according to embodiments are applicable. In aradio front end circuit used for example in a 3GPP LTE radio, amultitude of bands may be used. Further, if for example carrieraggregation where separate bands are collected and used simultaneouslyin different configurations, versatility is a key to a feasible frontend solution. Still further, if the front end should be usable for otherradio access technologies as well, such as GSM, UMTS, WLAN, GNSS, etc.,the demands on versatility further increases. The received signal canthus be in a multitude of frequencies and having a wide or narrowbandwidth, and for example, a band selection filter, or another circuitthat needs a resonator, may need to be configurable for this dependingon current operating mode. Variable capacitance in such band selectionfilters normally do a lot, e.g., by using capacitor banks wherecapacitance can be switched in on demand, but by using a tunableinductor as demonstrated above, versatility can be improved, as well asthe performance of circuits including resonators. For example, by usingsuch resonators for band selection filters in multi-band receivers, theexpanded tunability of the filters can make the band selection filterusable for any band of the multi-band receiver. By using one or moretunable inductor arrangements 602, 604 as those demonstrated above, thedemands on versatility can be met. Flexible band combinations arethereby enabled.

An example where the front end arrangement as demonstrated above can beused is a multiband radio frequency receiver 600. The receiver 600comprises a first receiver path arranged to receive a radio signal in afirst frequency band and a second receiver path arranged to receive aradio signal in a second frequency band, wherein the first frequencyband operates at a higher frequency than the second frequency band,i.e., a high-low band arrangement where both the high and the low bandscan be received simultaneously. Each of the first and second receiverpaths can be arranged to selectively operate at a selected frequencyband among a plurality of frequency bands, e.g., the first high-bandpath can select to operate in one of 1800 MHz, 1900 MHz, 2100 MHz and2700 MHz frequency bands while the second low-band path can select tooperate in one of 750 MHz, 850 MHz, 900 MHz and 1500 MHz frequency bandssimultaneously. These frequency bands are only demonstrated as examples,and other frequency bands and groupings between high and low-frequencybands are equally possible. Each receiver path comprises a resonatorcomprising a tunable inductor arrangement 602, 604 as demonstratedabove, wherein the resonators are arranged to be tuned for the selectedfrequency band in respective receiver path. Arrangements with more thantwo such receiver paths are also possible. Flexible frequency bandcombinations are thus enabled, which for example is advantageous incarrier aggregation solutions since each filter can be enabled to coverany frequency within the total frequency range of the receiver 600 dueto the improved tenability of the filters.

FIG. 6 illustrates an example where the resonator when used for tuningLNA output. The resonator with tunable inductor arrangement can, ofcourse, be used for other purposes as well, such as for filters,impedance matching, etc., where a tunable inductance can be used.

FIG. 7 is a block diagram schematically illustrating communicationdevice 700 according to an embodiment. The communication devicecomprises a receiver or transceiver 702, which can be connected to anantenna 704, and other circuits 706 such as a processor arranged tointeract with the receiver or transceiver 702, input and outputinterfaces of the communication device 700, etc. The receiver ortransceiver 702 comprises a resonator 710, wherein the resonatorcomprises one or more tunable inductor arrangements according to any oneof embodiments demonstrated above. The tunable inductor arrangement istunable to enable the resonator 710 to work at a plurality of resonatingfrequencies. The receiver or transceiver can also comprise a controller708 which can be arranged to control the tuning of the resonator 710,i.e., also the tunable inductor arrangement. The receiver 702 can, forexample, be the multiband radio frequency receiver 600 demonstrated withreference to FIG. 6 .

FIG. 8 is a flow chart schematically illustrating a method of a tunableinductor arrangement according to an embodiment. The method comprisesdetermining 801 a tuning setting for the tunable inductor arrangement.This can be made by receiving frequency allocation from a remote entityor from an entity within a communication apparatus having the tunableinductor arrangement. Based on for example the frequency allocationinformation switch states are assigned 802 for the switch or respectiveswitches for the tuning setting and controlling 803 the switchesaccording to the assigned switch states. Upon a new allocation, theprocedure can be repeated.

The method according to the present invention is suitable forimplementation with the aid of processing means, such as computersand/or processors, especially for the case where a digital controllercontrols the transceiver. Therefore, there is provided computerprograms, comprising instructions arranged to cause the processingmeans, processor, or computer to perform the steps of any of the methodsaccording to any of the embodiments described with reference to FIG. 8 .The computer programs preferably comprise program code which is storedon a computer readable medium 900, as illustrated in FIG. 9 , which canbe loaded and executed by a processing means, processor or computer 902to cause it to perform the methods, respectively, according toembodiments of the present invention, preferably as any of theembodiments described with reference to FIG. 8 . The computer 902 andcomputer program product 900 can be arranged to execute the program codesequentially where actions of the any of the methods are performedstepwise. The processing means, processor, or computer 1002 ispreferably what normally is referred to as an embedded system. Thus, thedepicted computer readable medium 900 and computer 902 in FIG. 9 shouldbe construed to be for illustrative purposes only to provide anunderstanding of the principle, and not to be construed as any directillustration of the elements.

The invention has mainly been described above with reference to a fewembodiments. However, as is readily appreciated by a person skilled inthe art, other embodiments than the ones disclosed above are equallypossible within the scope of the invention, as defined by the appendedpatent claims.

What is claimed is:
 1. A substrate having a tunable inductor arrangementarranged thereon, the tunable inductor arrangement comprising: a tunableinductor comprising: a plurality of winding parts; and a switcharrangement switchable between: a first switch setting thatinterconnects the plurality of winding parts such that parallel groupsof winding parts are connected in series between first and second inputsof the tunable inductor arrangement; and a second switch setting thatinterconnects the plurality of winding parts in series between the firstand second inputs.
 2. The substrate of claim 1, wherein the parallelgroups comprise a first parallel group of winding parts connected inseries between the first and second inputs with a second parallel groupof winding parts.
 3. The substrate of claim 2, wherein the switcharrangement provides a virtual ground connection at the seriesconnection between the first parallel group and the second parallelgroup.
 4. A radio frequency transceiver comprising a resonator, whereinthe resonator is arranged on the substrate of claim 1, and wherein thetunable inductor arrangement is tunable for changing the resonatingfrequency of the resonator.
 5. The substrate of claim 1, wherein thesubstrate is a chip.
 6. The substrate of claim 1, wherein the substrateis a printed circuit board.
 7. The substrate of claim 1, wherein theplurality of winding parts comprises: a first winding part connected atone end to the first input; a second winding part connected at one endto the other end of the first winding part; a third winding partconnected at one end to the second input; a fourth winding partconnected at one end to the other end of the third winding part; whereinthe first, second, third and fourth winding parts are interleaved on thesubstrate such that magnetic fields of the windings are essentiallycommon.
 8. The substrate of claim 7, wherein the first switch settinginterconnects the first and fourth winding parts in parallel and thesecond and third winding parts in parallel, with the parallel couplingsconnected in series between the first and second inputs, and wherein thesecond switch setting interconnects the first, second, fourth and thirdwinding parts in series between the first and second inputs.
 9. Acommunication device comprising: a radio frequency transceiver thatincludes a substrate having a tunable inductor arrangement arrangedthereon, for frequency tuning of the radio frequency transceiver, thetunable inductor arrangement comprising: a plurality of winding parts;and a switch arrangement switchable between: a first switch setting thatinterconnects the plurality of winding parts such that parallel groupsof winding parts are connected in series between first and second inputsof the tunable inductor arrangement; and a second switch setting thatinterconnects the plurality of winding parts in series between the firstand second inputs.
 10. The communication device of claim 9, wherein theradio frequency transceiver includes a multi-band radio frequencyreceiver, the multi-band radio frequency receiver comprising: a firstreceiver path arranged to receive a radio signal in a first frequencyband; a second receiver path arranged to receive a radio signal in asecond frequency band; wherein the first frequency band operates at ahigher frequency than the second frequency band; and wherein each of thefirst and second receiver paths is arranged to selectively operate at aselected frequency band among a plurality of frequency bands, andwherein the tunable inductor arrangement is tuned for the selectedfrequency band.